How Are Outwash Plains Formed?

outwash-plains-formed Credit: Nick/CC-BY-2.0

Outwash plains form when melt from glaciers deposit sand, sediments, gravel and clay along broad, sloping land. These landforms can be created quickly due to rapid water action and are often several layers thick due to irregular water flow from seasonal melting and refreezing.

Larger volumes of water and faster melting lead to large outwash plains. Smaller particles of sediment are carried further away from the glacier whereas larger pieces of gravel and clay coalesce closer to the edge of remaining ice.

Some outwash plains are several hundred feet thick in sediment deposits. Scientists can study the layers in these plains to gather data concerning the movement of glaciers over time. Ice itself can be buried in outwash debris if the glacier advanced and then retreated only to leave lower layers of ice behind. This happens because of rapid melting on a glacier's top but slower melting closer to the ground.

Many areas of Michigan are remnants of outwash plains from the last ice age more than 10,000 years ago, according to Michigan State University. These flat, fertile areas of land are great for growing crops thanks to nutrient-rich soil left behind after glaciation. Sand and gravel mining often occur in outwash plains as rich deposits of such material cover large areas.